Lymphokines (lymphocyte mediators) are substances produced by antigenically- or mitogenically-stimulated lymphocytes which play a crucial role in cellular immunity, an important defense mechanism against infectious diseases and cancer. These substances include macrophage inhibitory factor (MIF), a lymphokine which confines macrophages at the site of inflammation, and macrophage activating factor (MAF), a lymphokine which activates macrophages to kill microorganisms and tumor cells. The proposed study has been designed to construct and characterize human lymphoid cell hybridomas producing large amounts of MIF and MAF. We propose to construct a number of T-T-cell hybrids secreting MIF and/or MAF by fusing human peripheral blood lymphocytes stimulated with mitogens with HAT-sensitive CEM-cells. We plan to select those hybrids which secrete large amounts of MIF and/or MAF and to establish growth and stimulation conditions for maximum production. We will characterize the MIF or MAF products of each selected hybrid by comparison with the previously characterized MIF and MAF species secreted by peripheral blood lymphocytes. This screening step will permit selection of hybrid cell lines which produce single characterized species of MIF or MAF. We plan to scale-up and grow these selected hybrid cell lines in bulk. Harvest of bulk supernatant from hybrid cell lines to be developed in this study combined with purification procedures previously established in our lab will make possible purification of MIF and MAF in quantities suitable for clinical testing and for biochemical characterization. These studies will make it possible to determine the effectiveness of MIF and MAF in the therapy of malignant and infectious diseases.